Catabolic regulation analysis of Escherichia coli and its crp, mlc, mgsA, pgi and ptsG mutants

Microbial Cell Factories

Research

Yuki Hirose¹  Dayanidhi Sarkar¹  Kazuyuki Shimizu²  Ruilian Yao³  Kenji Nakahigashi⁴  Qin Ye⁵ 

[1]Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, 820-8502, Iizuka, Fukuoka, Japan

[2]Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, 820-8502, Iizuka, Fukuoka, Japan

[3]Institute of Advanced Bioscience, Keio University, 997-0017, Tsuruoka, Yamagata, Japan

[4]Department of Bioscience and Bioinformatics, Kyushu Institute of Technology, 820-8502, Iizuka, Fukuoka, Japan

[5]State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 200237, Shanghai, China

[6]Institute of Advanced Bioscience, Keio University, 997-0017, Tsuruoka, Yamagata, Japan

[7]State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 200237, Shanghai, China

关键词: Xylose;    Transcript Level;    Dilution Rate;    Glucose Consumption Rate;    Glucose Uptake Rate;   

DOI  :  10.1186/1475-2859-10-67

 received in 2011-01-31, accepted in 2011-08-11,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundMost bacteria can use various compounds as carbon sources. These carbon sources can be either co-metabolized or sequentially metabolized, where the latter phenomenon typically occurs as catabolite repression. From the practical application point of view of utilizing lignocellulose for the production of biofuels etc., it is strongly desirable to ferment all sugars obtained by hydrolysis from lignocellulosic materials, where simultaneous consumption of sugars would benefit the formation of bioproducts. However, most organisms consume glucose prior to consumption of other carbon sources, and exhibit diauxic growth. It has been shown by fermentation experiments that simultaneous consumption of sugars can be attained by ptsG, mgsA mutants etc., but its mechanism has not been well understood. It is strongly desirable to understand the mechanism of metabolic regulation for catabolite regulation to improve the performance of fermentation.ResultsIn order to make clear the catabolic regulation mechanism, several continuous cultures were conducted at different dilution rates of 0.2, 0.4, 0.6 and 0.7 h-1 using wild type Escherichia coli. The result indicates that the transcript levels of global regulators such as crp, cra, mlc and rpoS decreased, while those of fadR, iclR, soxR/S increased as the dilution rate increased. These affected the metabolic pathway genes, which in turn affected fermentation result where the specific glucose uptake rate, the specific acetate formation rate, and the specific CO2 evolution rate (CER) were increased as the dilution rate was increased. This was confirmed by the 13C-flux analysis. In order to make clear the catabolite regulation, the effect of crp gene knockout (Δcrp) and crp enhancement (crp+ ) as well as mlc, mgsA, pgi and ptsG gene knockout on the metabolism was then investigated by the continuous culture at the dilution rate of 0.2 h-1 and by some batch cultures. In the case of Δcrp (and also Δmlc) mutant, TCA cycle and glyoxylate were repressed, which caused acetate accumulation. In the case of crp+ mutant, glycolysis, TCA cycle, and gluconeogenesis were activated, and simultaneous consumption of multiple carbon sources can be attained, but the glucose consumption rate became less due to repression of ptsG and ptsH by the activation of Mlc. Simultaneous consumption of multiple carbon sources could be attained by mgsA, pgi, and ptsG mutants due to increase in crp as well as cyaA, while glucose consumption rate became lower.ConclusionsThe transcriptional catabolite regulation mechanism was made clear for the wild type E. coli, and its crp, mlc, ptsG, pgi, and mgsA gene knockout mutants. The results indicate that catabolite repression can be relaxed and crp as well as cyaA can be increased by crp+, mgsA, pgi, and ptsG mutants, and thus simultaneous consumption of multiple carbon sources including glucose can be made, whereas the glucose uptake rate became lower as compared to wild type due to inactivation of ptsG in all the mutants considered.

【 授权许可】

Unknown   
© Yao et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.